1. Field of the Invention
The present general inventive concept relates to a toner usable in electrophotography or electrostatic image development.
2. Description of the Related Art
It is difficult to provide precise control of the particle size and the geometric size distribution of toner by using a pulverizing process in the manufacturing method of toner suitable for an electrophotographic process or an electrostatic image recording process. Also, it is difficult to separately control the major characteristics of toner, such as charging characteristics, fixability, flowability, and preservation characteristics, by using a pulverizing process. In particular, toner needs to have a small particle size and a narrow geometric size distribution to obtain an image of high quality, but it is difficult to provide such toner by using a pulverizing process. Also, it is very difficult to control a toner particle internal structure to allow both a high gloss property and a large fixing area of toner by using a pulverizing process.
Alternatively, an aggregating process is suggested to solve the problems of a pulverizing process. In an aggregating process, binder resin latex particles, pigment particles, and wax particles are first prepared, and then toner particles are formed by aggregating the binder resin latex particles, pigment particles, and wax particles together. In an aggregating process, a shape and an internal structure of the toner particles are relatively easy to control, but controlling uniformity of a shape of the toner particles in relation to geometric size distribution of the toner particles is still difficult. That is, controlling a shape of the toner particles is facilitated when a particle size of the toner is greater than the average particle size, but a shape of the toner particles is closer to a sphere shape than a desired shape when a particle size of the toner is smaller than the average particle size. Toner particles of a sphere shape may cause degradation in cleaning performance of a cleaning blade during an electrophotography process.
In order to satisfy recent demands in printing such as high-speed printing, high-quality image printing, and environment friendly printing, toner having improved durability, improved fixability, or improved environmental properties is needed. Since a shearing stress is applied to the toner many times due to the high-speed printing, the toner needs to be designed to have a high durability. At the same time, the toner needs to be designed to have high gloss and a large fixing area to obtain a printing image of high quality. Such characteristics of the toner are expected to be significantly affected by a shape and surface characteristics of the toner particles.
Anti-offset properties of toner serve an important role by allowing the toner to have a large fixing area. Silicon oil may be coated on a fixing roller to improve the anti-offset properties of the toner. However, in this case, an oil tank and other related devices are needed. Also, degradation of the fixing roller is promoted, and thus frequent maintenance is necessary. Alternatively, a method of adding wax to toner is generally used to improve the anti-offset properties of the toner. The anti-offset properties of the toner are expected to change according to the wax and composition of a binder on a surface of the toner.
A method of adding an external additive including silica particles to a surface portion of the toner particles is used to improve charging stability, transferring efficiency, and cleaning properties. The external additive improves feeding characteristics of the toner by adding flowability to the toner particles. Also, the external additive may add charging stability to a surface portion of the toner particles. Moreover, the external additive may improve cleaning characteristics of the toner. That is, the external additive reduces adhesion force of the toner particles to a surface of an electrostatic latent image carrier, and thus remaining toner may be easily removed. However, using the external additive may be a factor that complicates control of surface characteristics of the toner particles.